This invention relates to a transformer construction with E-shaped and I-shaped magnetic cores and in particular to spacer members for a transformer, and to a method of manufacturing the transformer.
A conventional transformer with E-shaped and I-shaped magnetic cores comprises an E-shaped magnetic core, an I-shaped magnetic core, primary and secondary coils, sheet insulators for insulating the coils from the cores, and spacer members for fixing the coils to the magnetic cores. The E-shaped magnetic core is formed from a stack of E-shaped laminations of magnetic material, and the I-shaped magnetic core is formed of I-shaped sheet laminations of magnetic material. The transformer of the above type is used, for example, for a high voltage transformer of a microwave oven. The sheet insulators cover the primary and secondary coils respectively. The spacer members, which are made of plastic for instance, are inserted into a gap defined between the coils and the cores to maintain the preferable distance after the sheet insulators are placed on the coils and after the coils are disposed on the cores.
The coils may be disposed in a predetermined position with respect to the magnetic cores. The spacer members also prevent the E-shaped sheet laminations from expanding, because the inner leg stack of the E-shaped core is not welded together.
However, if one side of the gap is larger than the other side because of shifting of the coils, it is difficult in practice for the spacer members to hold the coil in a preferable or desired position for a long period of time and completely avoid expansion of the E-shaped sheet laminations inasmuch as the spacer members are inserted into the gap after the disposition of the coils. Therefore, in such prior art arrangements, vibrations of the laminations of the inner leg causes undesirable noise.